Re-settable locking mechanism for downhole tools

ABSTRACT

The present invention generally comprises a tubular body which is adapted to be attached to a drill string, where the body defines a bore therethrough which accommodates a piston slidably disposed between a first and second position. This piston is aligned generally normally respect to an actuating piston and an expandable tool. This piston is actuated by hydraulic pressure which moves the piston from a first, biased position to a second position where it engages the actuating piston of expandable tool to lock the piston in a locked or closed position. The flow restrictor serves to create a selected time delay before the piston is exposed to an increase in hydraulic pressure within the borehole. In such a fashion, an increase in hydraulic pressure in the borehole will overcome the bias of the piston only where the pressure is maintained for a selected period of time. The hydraulic pressure at which the piston in the locking mechanism overcomes the spring bias is substantially less than the pressure necessary to overcome this spring bias of the piston and the expandable tool.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to downhole drilling and reaming tools. More specifically, the present invention relates to a locking mechanism selectively actuable in response to input from the surface operator for securing an expandable downhole tool in a closed or locked position.

2. Description of the Prior Art

Various methods have been devised for passing a drilling assembly through an existing cased borehole and permitting the drilling assembly to drill a new borehole that is of a larger diameter than the inside diameter of the existing upper cased borehole. One such method uses an under-reamer, which is collapsed to pass through the smaller diameter existing, cased borehole and then expanded to ream the new, larger diameter borehole for the installation of larger diameter casing. Another method is the use of a winged reamer disposed above a conventional bit.

Under-reamers usually have hinged arms with attached cutters. The tool typically has pocket recesses formed in the body where the arms are retracted when the tool is in a closed state. Most of the prior art under-reamers utilize swing out cutter arms that are pivoted at an end opposite the cutting end of the reamer and are actuated by mechanical or hydraulic forces acting on the arms to extend or retract them. Some examples of these types of under-reamers are shown in U.S. Pat. Nos. 3,224,507; 3,425,500; and 4,055,226.

An example of a hydraulically expandable, concentric reaming tool is the RHINO reamer manufactured by Smith International, Inc. The tool includes three cutter blocks that are equally spaced around the tool circumference and carrying PDC cutting elements. The cutter blocks are extended from a collapsed position by hydraulic actuation. The cutter blocks include a stabilizer gauge pad and a formation cutting structure. A lock-up system restricts fluid from actuating the cutter blocks during shoe track drill out.

Another example of a hydraulically expandable, concentric reaming tool is that described in U.S. Pat. No. 6,622,803B2 which describes a tubular body for connection to a drill string and or rotatable sleeve carried about the tubular body and movable between an inactive and active positions. The sleeve is moved from the inactive position by a hydraulic piston which, upon the application of fluid pressure, retracts a piston from a key slot so that the sleeve may move to the active position upon rotation of the drill string.

Another example of a hydraulically expandable, concentric reaming tool is the REAMASTER reamer also manufactured by Smith International, Inc. This tool is illustrated in U.S. Pat. No. 4,431,065, which describes it as having a tubular body for connection to a drill string and a cutting arm received within a recess in the tubular body. The cutting arm is moved between a retracted position approximately aligned with the axis of the tubular body and a deployed position extending laterally outwardly of the body by a hydraulic plunger that actuates the cutting arms from a fully retracted to a fully deployed position.

An example of a mechanically actuated expandable drill bit that does not use pivoting cutter arms to ream a borehole is shown in U.S. Pat. No. 3,365,010. Blades with cutters ride in opposed, axially oriented channels angled with respect to the axis of the tool. When the blades impact the bottom of the borehole, shear pins retaining the blades are broken allowing the blades to move up the channels thereby expanding out against the borehole wall for subsequent borehole enlargement. A large pin for each blade retains the expanded blades in a desired position to control the gage of the borehole. When the expandable drill bit is tripped out of the borehole, the blades fall down the angled tracks through frictional and gravitational forces.

The under-reamer shown in U.S. Pat. No. 3,433,313 has a tubular body with a sleeve movably positionable therein and adapted to move responsive to the pressure of drilling fluid. Movement of the sleeve deploys the cutters to their cutting position. The sleeve is moved in the opposite direction with a wireline tool to retract the cutters from their cutting position and also stop the flow of drilling fluid to allow retraction of the cutters.

An expandable under-reamer is disclosed in U.S. Pat. No. 6,378,632 having an under-reamer body forming at least a pair of opposed downwardly and inwardly angled slots. Fluid is circulated through the under-reamer body. At least a pair of cutter assemblies housed within the under-reamer body is adapted to engage in the opposed angled slots formed by the under-reamer body. Each cutter assembly consists of a cutter support body having a track at a first end, a piston at a second end, and cutters formed in between the ends. The piston slides within a sleeve formed in the under-reamer body and extending parallel with the angled slots formed in the under-reamer body. The sleeve is in fluid communication with a control port formed in the under-reamer body. Fluid under pressure, when admitted to the piston sleeve below the piston, drives the cutter assembly upwardly and outwardly along the angled slots to commence an under-reaming operation. A spring in the under-reamer body retracts the cutter assemblies when fluid is shut off at the control port. The hydraulically operated under-reamer opens a borehole below a restriction that is larger than the restriction itself. The under-reamer has a cutter system with a pair of cutters that engage the formation by traversing upward and outward along a track that is angled with respect to an axis of the under-reamer body. The cutters are forced to the extended position by a piston built into each cutter support. Pressure acting on the piston comes from the pressure differential between the annulus and the drill string during circulation of the drilling fluid.

A related type of tool available from Halliburton Security DBS is the “Near Bit Reamer”. The tool is designed to open the borehole to a larger diameter than the pilot bit. Once the tool is below the casing shoe, the reamer blades are hydraulically actuated. The “Near Bit Reamer” is adapted for use just above the drill bit or above a rotary steerable system. Also available from Halliburton Security DBS is the XL2 Series under-reamer. This tool can be provided as an expandable stabilizer and is run in conjunction with an under-reamer for better stability. The arms are opened hydraulically and closed mechanically by a return spring.

Another tool described as an eccentric adjustable diameter blade stabilizer is shown in U.S. Pat. No. 6,227,312. The eccentric stabilizer is adapted for mounting on a bi-center bit having an eccentric reamer section and a pilot bit. A pair of adjustable stabilizer blades is recessed within openings in a housing. The blades are radially extended by a camming action produced upon axial movement. An extender piston causes the blades to radially extend and a return spring causes the blades to retract.

As set forth above, expandable drilling and stabilizing tools offer a number of advantages. One of the disadvantages of such tools, however, is the ability to selectively lock the tool in a closed or locked position both before the tool is tripped in the borehole as well as when the tool is ready to be retrieved from the borehole. The ability to selectively lock an expandable tool is significant in several respects. Hydraulically actuated, expandable tools are designed to return to their “reset” or closed position upon a reduction in hydraulic pressure. Fluctuations in hydraulic pressure in the borehole, however, may unintentionally actuate the tool. Therefore, the closed or open posture of the tool may not be known until the tool is returned to the surface or, alternatively, when the drill string becomes caught below a restricted portion in the casing in which case the tool, the casing and even the drilling rig may be damaged.

Yet other disadvantages of prior art locking mechanisms, e.g. rupture disks or shear pins, have only a one-time use and thus have limited application should it be necessary to expand the reaming or stabilizing features more than once when run in the borehole.

Another disadvantage of prior systems is the inability of independent actuation in the borehole. In this connection, when a series of expandable tools is incorporated in the drilling string, it is often difficult to actuate some but not all of the tools for a given application.

SUMMARY OF THE INVENTION

The present invention addresses the above and other disadvantages of prior expandable reamer and stabilizers by providing a mechanism to selectively lock an expandable tool in a closed or “locked” position after the tool has been run in the borehole.

Expandable downhole tools generally employ an actuating piston which is spring biased in a position consistent with the closed position of the cutter arm or stabilizer. This spring bias is overcome when a selected hydraulic pressure is applied to the piston. Hence, the piston, and thus the cutting arm or stabilizer, is moveable between a first (closed) and second (open) position depending on the application or removal of hydraulic pressure. In application, fluid circulation is initiated once the tool is run in the borehole in a “closed” position to increase fluid pressure beyond a selected value. This increase in fluid pressure serves to overcome the spring bias of the actuating piston which in turn acts on the cutting arm or stabilizer to bring it to an expanded or “open” orientation.

One embodiment of the invention comprises a tubular body which is adapted to be attached to a drill string, where the body defines a bore therethrough which accommodates a piston slidably disposed between a first and a second position. This piston is aligned generally normally with respect to the actuating piston in the expandable tool. This piston is actuated by hydraulic pressure which moves the piston from a first, biased position to a second position where it engages the actuating piston of the expandable tool to lock said piston in a locked or closed position.

In the aforedescribed embodiment, the piston in the locking mechanism is exposed to borehole hydraulic pressure through a flow restrictor. The flow restrictor serves to create a selected time delay before the piston is exposed to an increase in hydraulic pressure within the borehole. In such a fashion, an increase in hydraulic pressure in the borehole will overcome the bias of the piston only where the pressure is maintained for a selected period of time.

The hydraulic pressure at which the piston in the locking mechanism overcomes the spring biasing force is substantially less than the pressure necessary to overcome the spring bias of the piston in the expandable tool. The operator can therefore be assured that the tool will always be locked in a closed position by a gradual increase in hydraulic pressure over a selected time period to a pressure below a selected value. In such a fashion, the tool may be resecured in a “locked” position while in the borehole.

In another embodiment, the actuation of the locking mechanism may be accomplished electrically via a series of electrical pulses. These pulses may be created, for example, by rotation or vertical manipulations of the drill string, which movement is sensed by sensors in the locking mechanism. Alternatively, these pulses may be created by fluid flow through the drill string. Pulses may also be created by that flow through the string. An electrical motor drives a pin to secure the actuating piston in a closed or locked position. A different but similar set of electrical impulses serves to reverse the electrical motor to withdraw the pin so as to allow the expandable tool to move to an expanded or open position upon the application of hydraulic pressure.

The present invention presents a number of advantages over prior art apparatus to lock or secure expandable tools in a desired orientation. One advantage is the ability to selectively lock the tool in a given position both at the surface and in the borehole. In such a fashion, fluctuations in borehole pressure will not serve to unexpectedly expand or open the tool in the borehole, thus resulting in the potential for an undesired expanded tool below a borehole constriction.

Another advantage is the ability of the various embodiments of the invention to be selectively relocked while the tool remains in the borehole. Yet another advantage is the ability of the present invention to be independently actuatable in the borehole.

Yet other advantages of the present invention will become apparent in light of the following description and figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 generally illustrates one embodiment of an expandable stabilizer as shown in an “open” or active position.

FIG. 2 illustrates the expandable stabilizer of FIG. 1 in a “closed” or pass-through orientation.

FIG. 3 illustrates a cross sectional view of the embodiment of the expandable stabilizer shown in FIGS. 1-2 with the inclusion of the locking mechanism of the present invention.

FIG. 4 illustrates a cross sectional, end view of the stabilizer shown in FIG. 1 in an “open” or “active” orientation.

FIG. 5 illustrates a cross sectional, end view of the reaming tool shown in FIG. 2 in a “closed” or “inactive” orientation.

FIG. 6 illustrates a block diagram of an electronic controller for the embodiment illustrated in FIGS. 10-1.

FIG. 7 illustrates a detailed, cross sectional view of an embodiment of the present invention as it would be applied to an expandable stabilizer in an unlocked position as the tool would be run in the borehole.

FIG. 8 illustrates a detailed, cross sectional view of the embodiment of the invention illustrated in FIG. 7 when the expandable tool is in an “active” or “open” position.

FIG. 9 illustrates a detailed, cross sectional view of the embodiment illustrated in FIG. 7 when the locking mechanism of the present invention is in an “engaged” or “locked” position.

FIG. 10 illustrates a detailed, cross sectional view of another embodiment of the invention as it would be applied to an expandable stabilizer.

FIG. 11 illustrates a detailed, cross sectional view of the embodiment illustrated in FIG. 10 in an “engaged” position.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A variety of expandable drilling and reaming tools have been developed. One such expandable tool is shown in FIGS. 1 and 2. FIGS. 1 and 2 illustrate an expandable stabilizer such as that disclosed in U.S. Pat. No. 6,622,803 as issued to Harvey, et al. These figures show an expandable tool 1 defining a pin end 4 and a box end 6 where pin end 4 is adapted for connection to a drilling string (not shown) and box end 6 is adapted for connection to a drilling tool (also not shown). The expandable tool embodies a series of stabilizer blades 10A-10B. Blades 10B are affixed to the body 2 of the tool 1, while blades 10B are affixed to a rotatable sleeve 3, as will be described in more detail below.

The expandable tool 1 is adapted to adopt an “open” and “closed” position for use in the borehole. FIGS. 2 and 5 illustrate the tool 1 in a “closed” position in which tool 1 would be run in the borehole past a constriction in the borehole where the tool would then be moved to an “open” position. In the “closed” position, sleeve 3 is rotated so as to align stabilizer blades 10A and 10B so as to present a minimum pass-through diameter.

FIGS. 1 and 4 illustrate the expandable tool in an “open” or “engaged” position. In this position, sleeve 3 and hence stabilizer blades 10A are rotated about body 2 such that blades 10A, in conjunction with fixed blades 10B, present a maximum diameter and hence greatest effectiveness for stabilizing the drill string. To achieve this “open” orientation, sleeve 3 is unlocked and the tool 1 is then rotated in the borehole whereby frictional forces acting on blade 10A rotate sleeve 3 thereby bringing blade 10A to their open orientation, as will be described below.

FIG. 3 illustrates a cross sectional view of the expandable tool of FIGS. 1 and 2 and as disclosed in U.S. Pat. No. 6,622,803. As disclosed in the '803 patent, the expandable tool 1 generally comprises a body 2 that accommodates one or more sleeves 3 which are rotatable about said body 2. One or more stabilizing blades 10A project radially from sleeve 3. Rotatable blade 10A is axially displaced from stationary blades 10B, as illustrated. Rotation of rotatable sleeve 3 causes the rotatable blade 10A to rotate in a common plane.

Tool 1 including body 2 and other components of the bottom hole assembly must be sized so as not to extend beyond the pass-through diameter defined by the overall tool. This allows the tool 1 to be tripped into the casing behind the down hole tool (not shown) without interference by blades 10A-10B, or other components of the bottom hole assembly. Consequently, when the rotatable blade 10A is aligned with stationary blades 10B, as shown in FIG. 2, the tool 1 can be lowered into a casing of a diameter that is less than the diameter of the bore formed by blades 10A and 10B when in a deployed position, as shown in FIG. 1.

With reference to FIGS. 3 and 7-8, when the rotatable blade 10A is in the inactive or closed orientation that is, aligned with stationary blades 10B—a key 60 mounted in a bore 155 in the tool body 2 engages a recess 115 (FIG. 8) formed in the inside surface of rotatable sleeve 3. Springs 111 urge key 60 radially outward into engagement with recess 115. Thus, the rotatable sleeve 3 is held in an inactive position to close blade 10A. Key 60 is attached by a connector 59 to one end of a main piston 102 that slides within a main piston housing 118 (FIG. 7) mounted within the tool body 2. A second key 61 is attached by another connector 67 to the other end of the piston 102.

When key 60 is retracted to release sleeve 3, frictional forces cause sleeve 3 to rotate relative to body 2. A circumferential groove (not shown) extending part-way around the inside surface of the sleeve 3 facilitates the sliding of the distal end of the second key 61 around the inside surface of sleeve 3. When the sleeve 3 has rotated approximately 180 degrees, key 61 reaches the recess 115 and the force on main piston 102 seats key 61 into recess 115 so that the rotatable sleeve 3 is held to maintain blade 10A in the open or “active” position.

While sleeve 3 is held against rotation, fluctuation in borehole fluid pressure may serve to displace piston 102 and thus allow key 61 to disengage from recess 115, which in turn permits sleeve 3 to rotate. Alternatively, these same fluctuations in fluid pressure may cause sleeve 3 to move from a “locked” to an “unlocked” position in the borehole. Thus, it is necessary to assure that the tool is in a given orientation at all times during drilling or reaming operations.

In FIG. 7 an embodiment of the locking mechanism 20 of the present invention is disclosed as it may be integrated into the expandable stabilizer 1 discussed above in relation to FIGS. 1-3. This hydraulically actuated locking mechanism generally comprises a deadbolt cylinder housing 22 defining a bore 24 therethrough. Housing 22 is adapted to be affixed within the bore 19 of expandable tool 1, as illustrated. In such a fashion, housing 22 is subject to mud pressure within the well bore through bore 19. Housing 22 defines a first end 26 which is situated in fluid communication with the drilling fluid through an aperture 28. Aperture 28 may be provided with a filter element 21 to prevent the introduction of large particulates which may be present in the drilling mud, e.g. cuttings. The second end 30 of housing 22 abuts and is secured to main piston housing 118 in a conventional manner, e.g. threaded fasteners. Alternatively, housing 22 may be welded to housing 118 or formed integrally during the manufacturing process. Bore 24 is aligned and connects with axial passage 120 formed in housing 118 so as to allow the axial reciprocation of deadbolt 34, as will be described below.

Bore 24 defines an internal shoulder 36 which serves as a physical stop to the downward reciprocation of a deadbolt actuating piston 40, which is disposed in bore 24 between shoulder 36 and a bulkhead 42. Bulkhead 42 is fixed in bore 24 between piston 40 and a floating piston 90. Floating piston 90 is slidably disposed in bore 24 and moves in response to fluid pressure, as will be described below. Piston 90 is provided with seals, e.g. o-ring seals, to prevent the bypass of fluid.

Bulkhead 42 is provided with a flow restrictor 52, such as a flow restrictor manufactured by Lee Company. Bulkhead 42 further includes a check valve 54, such as a valve also manufactured by Lee Company. A substantially non compressible fluid, e.g. hydraulic oil, is contained within the spaces defined above and below bulkhead 42. When pressurized, fluid is forced through flow restrictor 52 so as to apply a displacing force on piston 40. When bore pressure is reduced, this fluid flows back through check valve 54 into reservoir 88 formed in bore 24 above bulkhead 42.

Drilling fluid introduced through bore 19 and aperture 28 acts on the exterior upper surface of floating piston 90. As this fluid pressure increases, piston 90 is displaced downwardly against bulkhead 42, thereby forcing pressurized hydraulic fluid through flow restrictor 52. This pressurized fluid then presents a downward force on piston 40. Piston 40 is biased in a disengaged or “open” position by a biasing element, e.g. a spring 68, which is disposed in an annular mounting channel 69 in housing 22, as illustrated. At a selected fluid pressure, the downward force acting on piston 40 overcomes the upward biasing force of spring 68. Piston 40 acts on deadbolt 34 to urge it downward into mating engagement with a deadbolt recess 80 formed in main piston 102. When deadbolt 34 is seated in recess 80, main piston 102 is then locked in a closed or “locked” position.

It is generally preferred that the biasing force provided by spring 68 be less than the biasing force provided by springs 105 and 111 in the expandable tool 1. In such a fashion, the locking mechanism may be engaged at a lower pressure than that necessary to actuate the expandable tool 1, as will be further described below.

Flow restrictor 52 enables a selective time delay to be manufactured into the operation of the locking mechanism of the present invention. Flow restrictor 52 includes a restricted flow path for hydraulic fluid from reservoir 88 when compared to that flow path for well fluid introduced through aperture 28 against piston 90. In such a fashion, restrictor 52 causes a delay in translating fluid pressure present in bore 19 to piston 40. As will be further explained below, this delay thus enables the main piston 102 to be locked before it can be displaced by fluid pressure.

The operation of this embodiment of the invention may be seen by reference to FIGS. 7-9. In FIG. 7, the locking device 20 is in a non-engaged or run-in position. Because borehole pressure is negligible, neither the main piston 102 nor the locking piston 40 have overcome the biasing force created by springs 68 and 105, respectively. FIG. 7 generally illustrates the configuration of the expandable tool 1 when run in the borehole to present a minimum pass-through diameter capable of passing through borehole obstructions, e.g. a casing shoe.

FIG. 8 illustrates a cross sectional view of the expandable tool and locking mechanism 20 when it is acted upon by a short term, non-gradual increase in downhole fluid pressure beyond a threshold pressure necessary to overcome the biasing force created by springs 105 and 1 1 1 in the expandable tool. Such pressure may be in the order of, for example, 300 psi. In this embodiment, well fluid acting on piston 102 has overcome the bias provided by springs 105 and 111 and laterally displaced piston 102 and keys 60 and 61. The lateral movement of key 60 out of groove 115 releases sleeve 3 to rotate about body 2 to the operative or “open” configuration illustrated in FIG. 1. Sleeve 3 is then locked into an open or operative position by the outward movement of key 61 into groove 115, as described above.

The sudden elevation of fluid pressure in the borehole to a selected level again, for example, 300 psi, is well in excess of that pressure necessary to overcome the biasing force created by spring 68. However, the time delay caused by hydraulic fluid passing through flow restrictor 52 prevents deadbolt 34 from engaging recess 80, and hence piston 112, before said piston 102 is laterally displaced out of alignment with said deadbolt 34, as described above. Hence, under the aforedescribed operating conditions, which can be rigidly controlled by the surface operator, tool 1 is now in an “open” orientation.

FIG. 9 illustrates a third state of the embodiment described above with respect to FIGS. 7 and 8. In this state, pressure in the well bore has been elevated to a value above that necessary to overcome the biasing effect of spring 68, e.g. 100 psi, but not high enough to overcome the biasing effect of springs 105 and 111. This lower pressure has been maintained at that value for a sufficient period of time, e.g. 180 seconds, so as to allow well fluid pressure applied to piston 90 to be translated to piston 40 which in turn moves deadbolt 34 to a downward or “engaged” position. Since borehole fluid pressure has not been elevated to a level high enough to overcome the bias of spring 105 and spring 111, main piston 102 and hence deadbolt recess 80 has not moved laterally out of axial alignment with deadbolt 34. Deadbolt 34 therefore moves into engagement in deadbolt recess 80, thereby locking piston 102 in a closed or “locked” position. Sleeve 3 is therefore prevented from rotating about body 2, and thus stabilizer 1 is maintained in a closed, pass-through orientation.

The configuration illustrated in FIG. 9 is that configuration which would be employed when the tool is prepared to be withdrawn from the borehole, or moved above or below a constricted zone in the borehole, which could not accommodate the enhanced diameter of the tool when sleeve 3 has been rotated to an open or deployed position. This locking and unlocking may be selectively accomplished an infinite number of times while the tool remains in the borehole.

The operation of this embodiment may be illustrated by the following example:

A bottom hole assembly consisting of a 10⅝×12¼″ bi center bit, a 10⅝×12¼″ bi-center stabilizer with a hydraulic deadbolt and a steerable mud motor with a 1¾ degree bend is run in the hole. The objective is to drill out the casing shoe through 11⅞″ casing and drill 3,000 feet of 12¼″ hole with a build in angle from 10 to 30 degrees at a direction of 55 degrees.

The string is tripped to the top of the cement at 14,527 feet and the deadbolt is locked by slowly bringing up pump pressure. 220 feet of cement inside the casing and 30 feet of open hole is drilled. The deadbolt must be reset twice when drill pipe connections are made during this interval.

The bi-center stabilizer is activated in the open hole and it is discovered that the hole is not completely enlarged. The bi-center stabilizer is deactivated and the deadbolt is reset. 30 feet more of open hole is drilled and the bi-center stabilizer is activated again. This time the hole is completely enlarged and the bi-center stabilizer is able to activate. The hole is drilled to total depth with no problems. All directional objectives are met with minimal sliding time.

The embodiment of the present invention illustrated in FIGS. 6 and 10-11 shows the same expandable tool 1 referenced above with respect to FIGS. 1-9. A housing 300 abuts and is secured to a main piston housing 388. Housing 300 defines a bore 302 therethrough housing a drive battery 304, such as a model TL-6526 lithium battery manufactured by Tadiran Inc. Battery 304 is coupled to a drive system controller 308 via electrical connectors 306 which pass through a bulkhead 307. Battery is monitored via battery monitor 421.

With reference to FIG. 6, controller 308 comprises a power regulator 401 such as a regulator manufactured by National Semiconductor. Regulator 401 is coupled to a microcontroller 405, such as a model PIC16F876A-ISO microcontroller manufactured by PIC Micro. Microcontroller 405 includes read only memory “RAM” 408 and non-volatile memory 410.

One or more accelerometers 412, such as a Model ADXL210AQC-1 accelerometer manufactured by Analog Devices is coupled to microcontroller 405. Accelerometer 412 senses rotation of the drill string in the borehole and sends a signal to microcontroller 405 to detect whether a series of rotations of the drill string matches a series of sequences preprogrammed in memory 410. Alternatively, accelerometer 412 can be programmed to sense the flow of fluids through the tool and in this fashion also provide a signal to microcontroller 405. In a preferred embodiment, one accelerometer 412 is mounted axially and a second mounted transverse to the axis of the drill string. Microcontroller 405 is isolated from undesired signals by a communication buffer 416.

A temperature sensor 414, such as a model TC1047AVNB Sensor manufactured by Texas Instruments, may be mounted in controller 308. Sensor 414 may be used as a diagnostic tool to evaluate the temperature at which the tool is operating at depth.

Memory 410 is programmed by the surface operator before the tool is tripped in the borehole by a conventional PC 500. In such a fashion, the surface operator has significant flexibility in those signals which may be used in operating the locking mechanism of the present invention. Alternatively, memory 410 may be programmed by the manufacturer.

Microcontroller 405 is coupled to an electrical stepper motor 310 such as a model LD II EAM-3A1 motor manufactured by EAD Motors of Dover, N.H. Motor 310 through motor gear box 429 rotates a drive spindle 312 which is threadedly received in a drive nut 324. Nut 324 terminates in a deadbolt 318 which is receivable in a deadbolt recess 380 formed in main piston 312 through passage 388 formed in piston housing 388. Deadbolt 318 is axially aligned with recess 380 when piston 312 has not been laterally displaced due to borehole pressure.

It is contemplated in this embodiment that the tool 320 will be run in the borehole with piston 312 disposed in a locked orientation with deadbolt 318 secured in recess 380. At a desired depth, the surface operator may unlock or disengage piston 312 by sending a series of preprogrammed signals to microcontroller 405, as discussed above. The downhole tool of claim 40.

FIG. 10 illustrates an expandable tool 1, e.g. a stabilizer, in an “expanded” or “open” position such as illustrated in connection with FIG. 8. FIG. 10 illustrates a cross sectional view of the expandable tool 1 and locking mechanism 320 as they would be acted on by an increase in down hole fluid pressure beyond a value necessary to overcome the biasing force created by springs 305 and 311. In this embodiment, well fluid acting on piston 312 has overcome the biasing force provided by springs 305 and 311 and laterally displaced main piston 312 and thus pins 360 and 361. The lateral movement of pin 360 out of groove 315 allows sleeve 303 to rotate about body 322 to the operative or “open” configuration illustrated in FIG. 1 upon rotation of tool body 322 in the borehole. Sleeve 303 is then locked into an “open” or operative position by the outward movement of pin 361 into said groove 315, as described above.

In the embodiment illustrated in FIG. 10, the surface operator has transmitted an electrical signal to the locking mechanism 320 which has released piston 312 to an “unlocked” position. As set forth above, this signal may take the form of a pre-select series of rotations of the drill string, the upward or downward movement of the drill string or the flow of fluid through the tool.

In a preferred embodiment, a time delay may be programmed into memory 410 to prevent inadvertent actuation of mechanism 320. In such a fashion, the surface operator is free to rotate the drill string or apply fluid pressure without the concern of actuating mechanism 320 and thereby placing piston 312 in an “unlocked” orientation.

FIG. 11 illustrates a cross sectional view of the expandable tool 1 in a “locked” position. This is the position of tool as it would ordinarily be run into the borehole. In this embodiment, circuit board 308, upon receipt of an electrical signal from the operator, activates drive motor 310 which in turn rotates drive spindle 314 into drive nut 324 thereby resulting in the downward displacement of deadbolt 318 into locking engagement in recess 380. At the surface, the locking of mechanism 320 may be accomplished via program instructions from PC 500. The locking of tool 320 in this fashion thus prevents the movement of sleeve 303 into an open position, in a manner consistent with that described above in association with the hydraulic embodiment.

The operation of this embodiment of the invention may be illustrated by the following example:

A packed hole bottom hole assembly consisting of a 12¼×14½″ bi-center bit, a 12¼″ bi-center stabilizer with an electronic deadbolt, a 30 foot drill collar, and a second bi-center stabilizer with electronic deadbolt is run in the hole. The objective is to drill out the casing shoe through 13⅜″ casing and drill 5,000 feet of 14½″ hole while maintaining angle at 30 degrees at a direction of 55 degrees.

The string is tripped to the top of the cement at 17,600 feet. The deadbolts were locked prior to running in the hole. 170 feet of cement inside the casing and 60 feet of open hole is drilled. The electronic deadbolts remain locked when drill pipe connections are made during this interval.

The bi-center stabilizers are activated in the open hole. After drilling 4,300 feet the hole angle has dropped 2 degrees below target. The uphole bi-center stabilizer is deactivated and selectively locked. The bottom hole angle will now build angle at 1-degree/100 feet. After 300 feet, the hole angle is back on target and the uphole bi-center stabilizer deadbolt is unlocked. The hole is drilled to total depth with no problems.

This second embodiment offers a number of advantages. One such advantage is the ability of this embodiment to lock or unlock the actuating piston without regard to hydraulic pressure which may act on hydraulic embodiment. This embodiment is also free of any constraints imposed by holding a given well bore pressure for a give period of time.

A second advantage is the ability of a series of locking mechanisms employed with a variety of expandable tools in a given drill string to be independently actuated based upon receipt of a variety of different signals from the surface operator. For example, a given mechanism may be programmed to actuate upon receipt of a given number of rotations “x” of the drill string, while other mechanism may actuate upon “10×” such rotations. In such a fashion, maximum flexibility is afforded to the surface operation.

Although particular detailed embodiments of the apparatus and method have been described herein, it should be understood that the invention is not restricted to the details of the preferred embodiment. Many changes in design, composition, configuration and dimensions are possible without departing from the spirit and scope of the instant invention. 

1. A locking mechanism for an expandable downhole tool which defines a pass-through diameter, said downhole tool including one or more elements which may be deployed from a first position defining a diameter less than or equal to the pass-through diameter to a second position defining a diameter which exceeds the pass-through diameter, the movement of said elements from said first to said second position occurring when well fluid under a first fluid pressure is applied for a time “t” to a first actuating piston disposed in a first bore formed in said tool such that said first piston moves from a closed to an unclosed position relative to said elements, said locking mechanism comprising: a body defining a second bore therein to accommodate a second piston where said second bore communicates with said first bore, said second piston being slidably disposed in said second bore between first and second positions where said piston is biased in said first position by a first biasing mechanisms; said second piston actuated when well fluid under a second fluid pressure is applied for a time “y” to overcome said first biasing mechanism so as to move said second piston to a second position to engage said first actuating piston so as to lock said elements in a first position; wherein said second pressure is less than said first pressure; and wherein said time “y” is greater than said time “t”.
 2. The locking mechanism of claim 1 further including a flow restrictor to create a time delay “y” at which fluid pressure may act on said second piston.
 3. The locking mechanism of claim 1 wherein the second piston is receivable in a recess formed in the first actuating piston of said downhole tool when said elements are disposed in a first position so as to prevent reciprocation of first piston in said first bore.
 4. The locking mechanism of claim 1 further including a third piston slidably disposed in said second bore, said third piston defining a surface exposed to well fluid, where said second and third pistons define a fluid chamber in said bore.
 5. The locking mechanism of claim 4 where said chamber is filled with a substantially non-compressible fluid.
 6. The locking mechanism of claim 4 further including a bulkhead disposed in said chamber between said second and third pistons where said bulkhead includes a flow restrictor and a check valve to regulate fluid flow through said bulkhead upon the application or release of well fluid pressure.
 7. The locking mechanism of claim 1 where the biasing means comprises a spring.
 8. The locking mechanism of claim 1 further including a deadbolt coupled to a first end of said second piston where said deadbolt is receivable in a recess formed in said first piston upon application of fluid pressure to a second end of said second piston.
 9. The locking mechanism of claim 1 wherein said first and second pistons are oriented transverse to each other.
 10. A locking system for a downhole tool which includes cutting or stabilizing elements moveable between an expanded and non-expanded orientation relative to a borehole where said elements are moved to said expanded orientation upon the application of well pressure beyond a value “p” as applied for a time “t”, where said pressure is applied to an actuating piston moveable in a first bore formed in a first body between a first and second orientation where in said second orientation said first piston urges or allows said elements to move to an expanded orientation, said body adapted to be coupled to a drill string, said locking system comprising: a second body defining a second bore therein to accommodate a second piston moveable between a first and second position, where said piston is biased in said first position by a biasing means; said second body coupled to said first body such that said first bore is disposed in communication with said second bore; said second first piston moveable to said second position by the application of a second fluid pressure applied for a time “y”; wherein in said second position said second piston engages said first piston so as to prevent said first piston from moving to said second position; where said second pressure is less than said first pressure; and where said time “y” is greater than said time “t”.
 11. The locking system of claim 10 further including a flow restrictor to create a time delay “y” at which fluid pressure may act on said second piston.
 12. The locking system of claim 10 wherein the second piston is receivable in a recess formed in the first actuating piston of said downhole tool when said elements are disposed in a non-expanded position so as to prevent reciprocation of first piston in said first bore.
 13. The locking system of claim 10 further including a third piston slidably disposed in said second bore, said third piston defining a surface exposed to well fluid, where said second and third pistons define a fluid chamber therebetween in said bore.
 14. The locking system of claim 13 where said chamber is filled with a substantially non-compressible fluid.
 15. The locking system of claim 13 where said chamber is comprised of a first and second chamber where said chambers communicate through a flow restrictor and a check valve upon the application or release of well fluid pressure as applied to said third piston.
 16. The locking system of claim 10 where the biasing means comprises a spring.
 17. The locking system of claim 10 where said first piston includes first and second end, where said first end terminates in a key receivable in a recess formed in said first piston upon application of fluid pressure to a second end of said second piston.
 18. The locking mechanism of claim 10 wherein said first and second pistons are oriented transverse to each other.
 19. A locking system for a downhole tool which includes cutting or stabilizing elements moveable between an expanded and non-expanded orientation relative to a borehole where said elements are moved to said expanded orientation upon the application of well pressure to an actuating piston moveable in a first bore formed in a first body between a first and second orientation where in said second orientation said first piston urges or allows said elements to move to an expanded orientation, said body adapted to be coupled to a drill string, said locking system comprising: a second body defining a second bore therein to accommodate a drive mechanism operable to move a locking pin between a first and second position; said second body coupled to said first body such that said first bore is disposed in communication with said second bore; said drive mechanism adapted to move said locking pin between said first and second positions upon the application of an electrical signal; wherein in said second position said locking pin engages the actuating piston so as to prevent said piston from moving to said second position.
 20. The locking system of claim 19 wherein said drive means comprises a stepper motor.
 21. The locking system of claim 19 wherein said drive means is actuated by an electrical battery
 22. The locking system of claim 19 further including sensor means operatively coupled to said drive mechanism.
 23. The locking system of claim 19 wherein the second piston is receivable in a recess formed in the first piston when said elements are disposed in a non-expanded position so as to prevent reciprocation of first piston in said first bore.
 24. The locking system of claim 19 further including a third piston slidably disposed in said second bore, said third piston defining a surface exposed to well fluid, where said second and third pistons define a fluid chamber therebetween.
 25. An expandable downhole tool which defines a pass-through diameter, said downhole tool including one or more elements which may be deployed from a first position defining a diameter less than or equal to the pass-through diameter to a second position defining a diameter which exceeds the pass-through diameter, the movement of said elements from said first to said second position occurring when well fluid under a first fluid pressure is applied for a time “t” to a first actuating piston disposed in a first bore formed in said tool such that said first piston moves from a closed to an unclosed position relative to said elements, said tool further comprising: a body defining a second bore therein to accommodate a second piston where said second bore communicates with said first bore, said second piston being slidably disposed in said second bore between first and second positions where said piston is biased in said first position by a first biasing mechanisms; said second piston actuated when well fluid under a second fluid pressure is applied for a time “y” to overcome said first biasing mechanism so as to move said second piston to a second position to engage said first actuating piston so as to lock said elements in a first position; wherein said second pressure is less than said first pressure; and wherein said time “y” is greater than said time “t”.
 26. The expandable tool of claim 25 further including a flow restrictor to create a time delay “y” at which fluid pressure may act on said second piston.
 27. The expandable tool of claim 25 wherein the second piston is receivable in a recess formed in the first actuating piston of said downhole tool when said elements are disposed in a first position so as to prevent reciprocation of first piston in said first bore.
 28. The expandable tool of claim 25 further including a third piston slidably disposed in said second bore, said third piston defining a surface exposed to well fluid, where said second and third pistons define a fluid chamber in said bore.
 29. The expandable tool of claim 28 where said chamber is filled with a substantially non-compressible fluid.
 30. The expandable tool of claim 28 further including a bulkhead disposed in said chamber between said second and third pistons where said bulkhead includes a flow restrictor and a check valve to regulate fluid flow through said bulkhead upon the application or release of well fluid pressure.
 31. The expandable tool of claim 25 where the biasing means comprises a spring.
 32. The expandable tool of claim 25 further including a deadbolt coupled to a first end of said second piston where said deadbolt is receivable in a recess formed in said first piston upon application of fluid pressure to a second end of said second piston.
 33. The expandable tool of claim 25 wherein said first and second pistons are oriented transverse to each other.
 34. A downhole tool which comprises cutting or stabilizing elements moveable between an expanded and non-expanded orientation relative to a borehole where said elements are moved to said expanded orientation upon the application of well pressure to an actuating piston moveable in a first bore formed in a first body between a first and second orientation where in said second orientation said first piston urges or allows said elements to move to an expanded orientation; said body adapted to be coupled to a drill string; a second body defining a second bore therein to accommodate a drive mechanism operable to move a locking pin between a first and second position; said second body coupled to said first body such that said first bore is disposed in communication with said second bore; said drive mechanism adapted to move said locking pin between said first and second positions upon the application of an electrical signal; wherein in said second position said locking pin engages the actuating piston so as to prevent said piston from moving to said second position.
 35. The downhole tool of claim 34 wherein said drive means comprises a stepper motor.
 36. The downhole tool of claim 34 wherein said drive means is actuated by an electrical battery.
 37. The downhole tool of claim 34 further including sensor means operatively coupled to said drive mechanism.
 38. The downhole tool of claim 34 wherein the second piston is receivable in a recess formed in the first piston when said elements are disposed in a non-expanded position so as to prevent reciprocation of first piston in said first bore.
 39. The downhole tool of claim 34 further comprising a third piston slidably disposed in said second bore, said third piston defining a surface exposed to well fluid, where said second and third pistons define a fluid chamber therebetween.
 40. A downhole tool adapted to be coupled to a drill string comprising: cutting or stabilizing elements moveable between an expanded and non-expanded orientation relative to a borehole where said elements are moved to said expanded orientation upon the application of well pressure beyond a value “p” as applied for a time “t”; said pressure being applied to an actuating piston moveable in a first bore formed in a first body between a first and second orientation; where in said second orientation said first piston urges or allows said elements to move to an expanded orientation; a second body defining a second bore therein to accommodate a second piston moveable between a first and second position, where said piston is biased in said first position by a biasing means; said second body coupled to said first body such that said first bore is disposed in communication with said second bore; said second first piston moveable to said second position by the application of a second fluid pressure applied for a time “y”; wherein in said second position said second piston engages said first piston so as to prevent said first piston from moving to said second position; where said second pressure is less than said first pressure; and where said time “y” is greater than said time “t”.
 41. The downhole tool of claim 40 further including a flow restrictor to create a time delay “y” at which fluid pressure may act on said second piston.
 42. The downhole tool of claim 40 wherein the second piston is receivable in a recess formed in the first actuating piston of said downhole tool when said elements are disposed in a non-expanded position so as to prevent reciprocation of first piston in said first bore.
 43. The downhole tool of claim 40 further including a third piston slidably disposed in said second bore, said third piston defining a surface exposed to well fluid, where said second and third pistons define a fluid chamber therebetween in said bore.
 44. The downhole tool of claim 43 where said chamber is filled with a substantially non-compressible fluid.
 45. The downhole tool of claim 43 where said chamber is comprised of a first and second chamber where said chambers communicate through a flow restrictor and a check valve upon the application or release of well fluid pressure as applied to said third piston.
 46. The downhole tool of claim 40 where the biasing means comprises a spring.
 47. The downhole tool of claim 40 where said first piston includes first and second end, where said first end terminates in a key receivable in a recess formed in said first piston upon application of fluid pressure to a second end of said second piston.
 48. The downhole tool of claim 40 wherein said first and second pistons are oriented transverse to each other. 